System and Method for Mitigating the Effects of Bit Insertion in a Communications Environment

ABSTRACT

A method for communicating data is provided that includes receiving a plurality of bits associated with a communications flow and determining whether one or more samples included in the flow should be suppressed. The method also includes suppressing a selected one or more of the samples if the selected samples are similar to previously received samples. The cell site element is further operable to invert one or more selected header bits. In a more particular embodiment, the bits to be inverted are part of a fixed length field and the inverted bits are odd. The inversion of the bits reduces packet overhead that is present in an HDLC communications environment.

TECHNICAL FIELD OF THE INVENTION

The present invention relates in general to the field of communicationsand, more particularly, to a system and a method for mitigating theeffects of bit insertion in a communications environment.

BACKGROUND OF THE INVENTION

Communication systems and architectures have become increasinglyimportant in today's society. One aspect of communications relates tomaximizing bandwidth and minimizing delays associated with data andinformation exchanges. Many architectures for effectuating proper dataexchanges can add significant overhead and cost in order to accommodatea large number of end-users or data streams. For example, a large numberof T1/E1 lines may be implemented to accommodate heavy traffic, but suchlines are generally expensive and, thus, usage of each one should bemaximized (to the extent that it is possible) in order to achieve asystem benefit per-unit of cost.

Compression techniques can be used by network operators to produce highpercentages of bandwidth savings. In certain scenarios, networkoperators may consider compressing common communication patterns thatappear on a given communication link. However, many of the existingcompression/suppression protocols are deficient because they are static,unresponsive, and rigid. Moreover, many such systems add overhead to thesystem with bit-insertion protocols, while not yielding a sufficientoffsetting bandwidth gain. Accordingly, the ability to provide acommunications system that consumes few resources, optimizes bandwidth,and achieves minimal delay presents a significant challenge for networkoperators, service providers, and system administrators.

SUMMARY OF THE INVENTION

From the foregoing, it may be appreciated by those skilled in the artthat a need has arisen for an improved suppression approach thatoptimizes data exchanges in a communications environment. In accordancewith one embodiment of the present invention, a system and a method forproviding protocols for dynamically suppressing data are provided thatsubstantially eliminate or greatly reduce disadvantages and problemsassociated with conventional compression/suppression techniques.

According to one embodiment of the present invention, a method forcommunicating data is provided that includes receiving a plurality ofbits associated with a communications flow and determining whether oneor more samples included in the flow should be suppressed. The methodalso includes suppressing a selected one or more of the samples if theselected samples are similar to previously received samples. The cellsite element is further operable to invert one or more selected headerbits. In a more particular embodiment, the bits to be inverted are partof a fixed length field and the inverted bits are odd. The inversion ofthe bits reduces packet overhead that is present in an HDLCcommunications environment: specifically in a zero-bit insertion schemefor HDLC.

Thus, the present invention is able to invert every other bit in apresence mask. This will prevent the HDLC zero bit insertions fromoccurring when five or more adjacent samples are included in a backhaulpacket. Certain embodiments of the present invention may provide anumber of technical advantages. For example, according to one embodimentof the present invention, a communications approach is provided thatminimizes the amount of overhead required to transmit GSMmux backhaulpackets. In one example implementation, this overhead can be reduced byup to fifty-one (51) bits per packet when the backhaul is fullyutilized. Reducing the overhead by 51 bits could allow up to three morevoice samples to be included in each backhaul packet without data lossdue to oversubscription. In many scenarios, about a 16.67% overheadreduction can be realized (i.e. removing 1 bit from 6 is ⅙=16.67%).

Other advantages are related to the underlying base solution, whichgenerally enhances bandwidth parameters for a given architecture. Thisis a result of the suppression scheme that yields bandwidth gains byrecognizing repetitious patterns. A given input bit stream may beidentified as a candidate for suppression. Subsequently, the bit patternis not transmitted over the backhaul, whereby the suppressed data can besimply played out or restored on the other end of the link.

Furthermore, the bandwidth savings can be produced without any increasein the complexity of multiplexing and demultiplexing schemes.Additionally, such an upgrade or enhancement may be provided to anexisting system with minimal effort. A simple algorithm may be used toleverage infrastructure already in place. Thus, a complete systemoverhaul is not necessary. Such advantages may be particularlybeneficial to service providers, as effective compression protocolssignificantly reduce their operating expenditures.

Note also that such an enhancement is flexible in that it can beextended to include a multitude of compressible, common, repetitivepatterns. Thus, such a solution can be easily extended to signaling andpacket data channels. This further allows such a configuration toaccommodate a wide range of incoming flows, as it may be extended to anumber of different types of traffic arrangements. Additionally, minimaloverhead is incurred as a result of the operations of the presentinvention.

Certain embodiments of the present invention may enjoy some, all, ornone of these advantages. Other technical advantages may be readilyapparent to one skilled in the art from the following figures,description, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is made to the following description takenin conjunction with the accompanying drawings, wherein like referencenumerals represent like parts, in which:

FIG. 1 is a simplified block diagram of a communication system fordynamically suppressing data in a network environment;

FIG. 2 is a block diagram of an example internal structure associatedwith either a cell site element or an aggregation node of thecommunication system;

FIG. 3 is a simplified schematic diagram of an example GSM 8.60 format;

FIG. 4 is a simplified schematic diagram of an example associated withthe communication system; and

FIG. 5 is a simplified flowchart illustrating an example flow associatedwith the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a simplified block diagram of a communication system 10 forsuppressing data in a communications environment. Communication system10 may include a plurality of cell sites 12, a plurality of mobilestations 13, a central office site 14, a plurality of base transceiverstations 16, a plurality of cell site elements 18, and a networkmanagement system 20. Additionally, communication system 10 may includean aggregation node 22, a plurality of base station controllers 24, amobile switching center 25, a public switched telephone network (PSTN)27, and an Internet protocol (IP) network 29. Note the communicationslinks extending between cell site element 18 and aggregation node 22, ascompared to the number of communication links extending between cellsite element 18 and base transceiver stations 16. This arrangement hasbeen provided in order to illustrate that without the present invention,the number of communication links between cell site 12 and centraloffice site 14 would be equal to the output of base transceiver stations16. By implementing the suppression techniques of the present invention(and as explained in detail below), a reduction in communication linksbetween cell site 12 and central office site 14 is achieved.

Communication system 10 may generally be configured or arranged torepresent 2.5G architecture applicable to a Global System for Mobile(GSM) environment in accordance with a particular embodiment of thepresent invention. However, the 2.5G architecture is offered forpurposes of example only and may alternatively be substituted with anysuitable networking system or arrangement that provides a communicativeplatform for communication system 10. For example, the present inventionmay be used in conjunction with data communications, such as those thatrelate to packet data transmissions. Additionally, communication system10 may be provided in a 3G network, where 3G equivalent networkingequipment is provided in the architecture. Communication system 10 isversatile in that it may be used in a host of communicationsenvironments such as in conjunction with any time division multipleaccess (TDMA) element or protocol for example, whereby signals fromend-users, subscriber units, or mobile stations 13 may be multiplexedover the time domain.

As illustrated in FIG. 1, in a GSM network, a backhaul network existsbetween a BTS and a BSC. The backhaul can be used to transmit voiceconversations, data, and control information using various standards andproprietary vendor specific formats. In order to address operationalexpenses, a backhaul optimization scheme is desired that will providesignificant bandwidth savings, while maintaining low latency andend-to-end transmissions for all possible frame types.

In accordance with the teachings of the present invention, communicationsystem 10 will invert every other bit in a presence mask. This willprevent HDLC zero bit insertions from occurring when several (e.g. 5) ormore adjacent samples are included in a backhaul packet. The advantagein such a scenario is that the amount of overhead required fortransmitting GSMmux backhaul packets can be reduced by up to fifty-one(51) bits per packet when the backhaul is fully utilized. Reducing theoverhead by 51 bits will allow up to three more voice samples to beincluded in each backhaul packet without data loss due tooversubscription. Other implementations may achieve greater savings suchthat even more voice samples can be included without data loss.

Additionally, an in accordance with the underlying base solution,communication system 10 operates to suppress unused, idle, and redundantinformation in offering an optimal solution for the backhaul network.This can be achieved by dynamically detecting and suppressing repeatingbit patterns embedded in subsequent 8 Kbps sub-rate frames and thenrecreating the suppressed data at the far end of the communicationslink. These operations can be performed regardless of the frame formatand the sub-rate width being employed at any given time. Thus, anincoming bit pattern may be evaluated to determine whether it can besuppressed. A bit pattern can be played out or restored on the oppositeend of the communication link to mimic the data in cases where the frameis designated for suppression. The restoration function includessuitable ordering and timing operations. This recognition (of prevalentrepeating streams) would allow the greatest savings for any compressionoperation. In cases where the incoming pattern is not a candidate forsuppression (i.e. not repetitious), the entire bit pattern could then besent, as the architecture would be unable to suppress all of the diversebit patterns in a given backhaul with fewer bits. A demultiplexer, whichis positioned downstream, may then simply perform a series of reverseoperations in identifying the suppressed information and playing out thedata.

Preprocessing of the input bits can be done such that the samples beingconsidered for suppression are not necessarily consecutive bits from theinput stream, but can be selected such that they are most likely to besuppressible. Hence, the present invention provides for the reorderingof input bits, the selection of samples from the reordered bit stream,and the restoration of proper bit ordering.

Using such a protocol, communication system 10 provides a simplisticsolution for reducing compression and decompression operations. Inaddition to creating minimal overhead and being easy to implement (withpotential modifications only being made to aggregation node 22 and cellsite element 18), such an approach could cooperate with any suitablecompression protocol or arrangement. The enhancement in transmission canbe provided in both aggregation node 22 and cell site element 18, as thepresent invention bi-directional.

Note that for purposes of teaching and discussion, it is useful toprovide some overview as to the way in which the following inventionoperates. The following foundational information may be viewed as abasis from which the present invention may be properly explained. Suchinformation is offered earnestly for purposes of explanation only and,accordingly, should not be construed in any way to limit the broad scopeof the present invention and its potential applications.

It can be appreciated that circuit switched data is generally present onthe backhaul and the challenge is to convert that into packet switcheddata such that additional IP traffic can be added to this data. Thiscould maximize the bandwidth available on the backhaul. From anotherperspective, the bandwidth required to support the circuit switched datashould be reduced where possible.

A number of time slots (e.g. within a T1/E1) are often idle or unused.Other patterns may include repetitive voice data, silence data, userdata, or control data. Recognizing this inefficiency allows some of thisidleness to be eliminated, as the only information that should bepropagating along the backhaul is information that is unique (i.e.cannot be recreated at aggregation node 22). Other insignificant datasegments (e.g. silence, certain control information, etc.) can similarlybe accounted for and eliminated from the traffic flows to produce anincrease in available bandwidth. The following are candidates forsuppression (i.e. not transmitted over a given IP E1 from BTS site toBSC site): 1) idle/unallocated time slots; 2) idle TRAU; 3) silenceTRAU; 4) error sub-rate/channel; 5) HDLC idle (repeating 7E flags); and6) GPRS idle/repeating PCU/CCU.

Hence, by removing much of the overhead, a new frame (or super-frame)can be built that is much smaller. The new frame can be packetized andthen sent across the backhaul. This would achieve a reduction inbandwidth required to communicate information from one location toanother and/or reduce the number of E1/T1 lines between base transceiverstation 16 and base station controller 24.

Mobile station 13 may be used to initiate a communication session thatmay benefit from such a suppression protocol. Mobile station 13 may bean entity, such as a client, subscriber, end-user, or customer thatseeks to initiate a data flow or exchange in communication system 10 viaany suitable network. Mobile station 13 may operate to use any suitabledevice for communications in communication system 10. Mobile station 13may further represent a communications interface for an end-user ofcommunication system 10. Mobile station 13 may be a cellular or otherwireless telephone, an electronic notebook, a computer, a personaldigital assistant (PDA), or any other device, component, or objectcapable of initiating a data exchange facilitated by communicationsystem 10. Mobile station 13 may also be inclusive of any suitableinterface to the human user or to a computer, such as a display,microphone, keyboard, or other terminal equipment (such as for examplean interface to a personal computer or to a facsimile machine in caseswhere mobile station 13 is used as a modem). Mobile station 13 mayalternatively be any device or object that seeks to initiate acommunication on behalf of another entity or element, such as a program,a database, or any other component, device, element, or object capableof initiating a voice or a data exchange within communication system 10.Data, as used herein in this document, refers to any type of numeric,voice, video, audio-visual, or script data, or any type of source orobject code, or any other suitable information in any appropriate formatthat may be communicated from one point to another.

Base transceiver stations 16 are communicative interfaces that maycomprise radio transmission/reception devices, components, or objects,and antennas. Base transceiver stations 16 may be coupled to anycommunications device or element, such as mobile station 13 for example.Base transceiver stations 16 may also be coupled to base stationcontrollers 24 (via one or more intermediate elements) that use alandline (such as a T1/E1 line, for example) interface. Base transceiverstations 16 may operate as a series of complex radio modems whereappropriate. Base transceiver stations 16 may also perform transcodingand rate adaptation functions in accordance with particular needs.Transcoding and rate adaptation may also be executed in a GSMenvironment in suitable hardware or software (for example in atranscoding and rate adaptation unit (TRAU)) positioned between mobileswitching center 25 and base station controllers 24.

In operation, communication system 10 may include multiple cell sites 12that communicate with mobile stations 13 using base transceiver stations16 and cell site element 18. Central office site 14 may use aggregationnode 22 and base station controllers 24 for communicating with cell site12. One or more network management systems 20 may be coupled to eithercell site 12 and central office site 14 (or both as desired), wherebymobile switching center 25 provides an interface between base stationcontrollers 24 (of central office site 14) and PSTN 27, IP network 29,and/or any other suitable communication network. Base transceiverstations 16 may be coupled to cell site element 18 by a T1/E1 line orany other suitable communication link or element operable to facilitatedata exchanges. A backhaul connection between cell site element 18 andaggregation node 22 may also include a T1/E1 line or any suitablecommunication link where appropriate and in accordance with particularneeds.

Base station controllers 24 generally operate as management componentsfor a radio interface. This may be done through remote commands to acorresponding base transceiver station within a mobile network. One basestation controller 24 may manage more than one base transceiver stations16. Some of the responsibilities of base station controllers 24 mayinclude management of radio channels and assisting in handoff/handoverscenarios.

In operation, various traffic protocols (e.g. time division multiplexed(TDM), GSM 8.60 Frame Relay, high level data link control (HDLC),asynchronous transfer mode (ATM), point to point protocol (PPP) overHDLC, TRAU, vendor-specific formats, etc.) may be used and communicatedby each base transceiver station 16 to cell site element 18 of cell site12. Cell site element 18 may also receive IP or Ethernet traffic fromnetwork management system 20. Cell site element 18 may multiplextogether payloads from the layer-two based traffic that have a commondestination. The multiplexed payloads, as well as any payloads extractedfrom the network management system IP or Ethernet traffic may becommunicated across a link to aggregation node 22 within central officesite 14. Aggregation node 22 may demultiplex the payloads for deliveryto an appropriate base station controller 24 or network managementsystem 20.

Mobile switching center 25 operates as an interface between PSTN 27 andbase station controllers 24, and potentially between multiple othermobile switching centers in a network and base station controller 24.Mobile switching center 25 represents a location that generally housescommunication switches and computers and ensures that its cell sites ina given geographical area are properly connected. Cell sites refergenerally to the transmission and reception equipment or components thatconnect elements such as mobile station 13 to a network, such as IPnetwork 29 for example. By controlling transmission power and radiofrequencies, mobile switching center 25 may monitor the movement and thetransfer of a wireless communication from one cell to another cell andfrom one frequency or channel to another frequency or channel. In agiven communication environment, communication system 10 may includemultiple mobile switching centers 25 that are operable to facilitatecommunications between base station controller 24 and PSTN 27. Mobileswitching center 25 may also generally handle connection, tracking,status, billing information, and other user information forcommunications in a designated area.

PSTN 27 represents a worldwide telephone system that is operable toconduct communications. PSTN 27 may be any landline telephone networkoperable to facilitate communications between two entities, such as twopersons, a person and a computer, two computers, or in any otherenvironment in which data is exchanged for purposes of communication.According to one embodiment of the present invention, PSTN 27 operatesin a wireless domain, facilitating data exchanges between mobile station13 and any other suitable entity within, or external to communicationsystem 10.

IP network 29 is a series of points or nodes of interconnectedcommunication paths for receiving and transmitting packets ofinformation that propagate through communication system 10. IP network29 offers a communications interface between mobile stations 13 and anyother suitable network equipment. IP network 29 may be any local areanetwork (LAN), metropolitan area network (MAN), wide area network (WAN),wireless local area network (WLAN), virtual private network (VPN), orany other appropriate architectural system that facilitatescommunications in a network environment. IP network 29 implements atransmission control protocol/Internet protocol (TCP/IP) communicationlanguage protocol in a particular embodiment of the present invention.However, IP network 29 may alternatively implement any other suitablecommunications protocol for transmitting and receiving data packetswithin communication system 10.

FIG. 2 is a simplified block diagram of an example internal structure ofcell site element 18 and aggregation node 22, both of which include adynamic suppression element 60. In one embodiment, dynamic suppressionelement 60 is an algorithm (potentially included in appropriatesoftware) that achieves the suppressing operations, along with themitigation of the effects of bit insertion, as described herein. Notethat these two functionalities may certainly be separated into separatemodules, or be resident in separate devices/boxes. Considerableflexibility is provided by the present invention and any such potentialarrangements may be based on particular communication needs and,furthermore, are clearly within the broad scope of the presentinvention. In this example architecture, the bit insertion issue isaddressed by dynamic suppression element 60.

The functional flow of communication system 10 may follow a bits in/bitsout protocol, being dependent only on the received bit pattern. InputDSOs may be demultiplexed to create an appropriate number of sub-rateDSOs, each corresponding to a different call. (Note that some DSOs arenot assigned to any call and still others are used for controlinformation.) For each sub-rate DS0, a certain portion (e.g. twomilliseconds) of samples may be collected synchronously. Because thecorresponding inputs are time-division multiplexed (TDM) streams, thecollection operation should be completed at roughly the same time. Forsixteen kilobits/sec multiplexing, this results in a collection of fourbytes of data from each stream at about the same time.

The collected samples may be compared to a few pre-identified (orpreviously learned) patterns (e.g. the previously occurring inputstreams) and decisions may be made regarding which bits are to besuppressed with a corresponding header representing that the data hasbeen suppressed. The receiving end may then perform reverse operationsin accounting for the suppression in order to restore the bit streamand, potentially, to then communicate it to its intended nextdestination. Thus, a demultiplexer/decompressor (not shown) may performtasks in reverse in order to undo what was done by the compressor andthe multiplexer, which can be included within aggregation node 22 and/orcell site element 18.

TDM streams may be TDM multiplexed to generate appropriate DSOs, whichare further combined with drop-and-insert DSOs to create T1/E1s. Basedon the header of the overall multiplexed packet, appropriate lineconditions or alarms may be generated at the output T1/E1 interface.Note that in order to increase robustness in the presence of errors, itis possible to protect payload header bits by a forward error correctingcode and dropping the cyclic redundancy check (CRC) from point to pointprotocol (PPP) frames. An example of a simple error correcting methodcould be a table-based parity method, which can correct all one-biterrors.

It is critical to note that dynamic suppression element 60 may bechanged considerably, as it offers only one example suppression protocolconfiguration that accommodates any of the identified incoming bitpatterns. Any number of alternative bit patterns may be readilyaccommodated by communication system 10 and are, therefore, included inthe broad scope of its teachings. These common patterns may be based onparticular communication needs or on the prevalence of commonlyreoccurring bit patterns in a given communications architecture.Additionally, any attached header bits may also provide E1/T1 lineconditions and alarms. In other embodiments, additional bits may beadded to the header bits in order to provide any number of functions,such as control parameters, the state of the given communication link,the condition of the E1/T1 line, the condition of an alarm, or theidentification of a certain packet. Thus, these extra bits may provideany suitable additional information that may be relevant to acommunication session occurring in communication system 10.Additionally, dynamic suppression element 60 can be used to transportany TDM stream over IP. For example, some applications use TDMA and GSMon the same E1 (i.e. TDM on some timeslots, GSM on others). The presentinvention transports all such information over IP and restores the bitstream on the far end of TDM E1. For some TDMA applications, there isnot a lot of suppression occurring, but the system is still functional.

Before turning to FIG. 3, it is critical to note that the use of theterms ‘aggregation node’ and ‘cell site element’ herein in this documentonly connotes an example representation of one or more elementsassociated with base transceiver station 16 and base station controller24. These terms have been offered for purposes of example and teachingonly and do not necessarily imply any particular architecture orconfiguration. Moreover, the terms ‘cell site element’ and ‘aggregationnode’ are intended to encompass any network element that is operable tofacilitate a data exchange in a network environment. Accordingly, cellsite element 18 and aggregation node 22 may be routers, switches,bridges, gateways, interfaces, or any other suitable module, device,component, element or object operable to effectuate one or more of theoperations, tasks, or functionalities associated with compressing dataand addressing bit insertion issues, as implied, described, or offeredherein.

As identified above, each of these elements may include software and/oran algorithm to effectuate suppression bit and insertion mitigation forvoice or packet data applications as described herein. Alternatively,such operations and techniques may be achieved by any suitable hardware,component, device, application specific integrated circuit (ASIC),additional software, field programmable gate array (FPGA), processor,algorithm, erasable programmable ROM (EPROM), electrically erasableprogrammable ROM (EEPROM), or any other suitable object that is operableto facilitate such operations. Considerable flexibility is provided bythe structure of cell site element 18 and aggregation node 22 in thecontext of communication system 10. Thus, it can be easily appreciatedthat such a function could be provided external to cell site element 18and aggregation node 22. In such cases, such a functionality could bereadily embodied in a separate component, device, or module.

FIG. 3 is simplified block diagram of an example GSM 8.60 format E1structure. In operation of an example embodiment, consider a case wherean end user is having a conversation using a mobile station. Voiceframes from a given mobile station are generally being generated every20 milliseconds in such a scenario. In a typical environment, there are320-bit frames that are sent directly behind each other. In a nativeenvironment, base transceiver station 16 receives this information andconverts it into TRAU frames. There is control information that isexchanged (on another channel) between base transceiver station 16 andbase station controller 24 (over an E1 link 40) that indicates whichchannel or which sub-rate that will be assigned for this call.

When a call comes up, these frames (which are primarily of a fixedlength) are put into T1/E1 sub-rates, whereby a DS0 is eight bits. Theseeight bits can be further divided into sub-rates (an 8 kilobit sub-ratecorresponds to a single bit, a 16 kilobit sub-rate corresponds to twobits, a 32 kilobit sub-rate corresponds to four bits, and a 64 kilobitsub-rate corresponds to the full DS0).

In a simple case, a call is on a 16 kilobit sub-rate channel and it willbe assigned to a time slot (and assigned one sub-rate inside that timeslot) for transmission over the E1. Every 125 microseconds, two bits ofthe frame are being sent across the E1. Base station controller 24receives this information, assembles the frames, and then presents themto the TRAU.

In accordance with the operation of the present invention, the framingprotocol that is used (e.g. 16 kilobit TRAU frames, half-rate calls,etc.) is ignored. The algorithm of the present invention willuniversally divide the channel into 8-kilobit sub-rates. In this manner,synchronization is not being attempted; only the raw bits are beingevaluated. The algorithm can begin to collect bits on an 8-kilobitsub-rate basis. For example, if a full E1 is present, then 31 time slots(each time slot having 8 sub-rates) are present that could have data.Hence, a total of 248 eight-kilobit sub-rates could be active.

In this example embodiment, an FPGA could be employed to monitor theline and to separate the bits into 248 sub-rates. The FPGA can alsocollect a sample that contains 16 bits for each sub-rate (every twomilliseconds). The FPGA can also perform demultiplexing operations.After the two-millisecond interval elapses, the FPGA then has 16 bitscollected for each sub-rate. The FPGA can then send an interrupt signalto IOS with this new packet (i.e. the super-frame) that has informationfor each of the sub-rates. From IOS, there will be 3968 bits (plusheader bits), which consists of 248 samples of 16 bits each.

Over a period of ten samples, that data would add up to approximately aframes worth of data. Recall that the frames are of a fixed length (e.g.160 bits). The algorithm can now take these and forward them to theother end (i.e. the base station controller) such that they can bedemultiplexed and regenerated. Coupled to this super-frame is a header,which can be a bit-mask (where there is one bit for each possible 16-bitsample). It should be noted that the bit mask is not always necessary(i.e. not included in the backhaul frame header). In order to compressthe data, the IOS records and saves ten samples (in a row) and thencompares the sample that is currently being evaluated with a sample thatoccurred ten samples ago. Stated differently, the algorithm compares thesample that it received for that sub-rate to the same sample that itreceived ten instances ago. Thus, the algorithm compares new bits tosimilar bits that would have been provided in the same bit position in aprevious frame. The present invention capitalizes on the intrinsicnature of the data and the inherent characteristics of the fixed lengthrestrictions.

The suppression changes dynamically based on the data that is beingcommunicated. In addition, protocols such as HDLC can be significantlyoptimized such that flags will synchronize or line-up such that they arecompressed out. Similarly, idle frames (or idle periods between frames)or silence will readily be compressed.

FIG. 4 is a simplified block diagram of an example that illustrates someof the concepts that have been discussed above. It should be emphasizedthat such an illustration is only a logical view of the presentinvention. Specifically, a single TRAU frame is generally not sent inthe same IP backhaul packet, as FIG. 4 suggests. FIG. 4 has only beenoffered for purposes of teaching and discussion. Indicated generally at62 are two TRAU frames being received by a router 70 (or a switch, agateway, etc.), which is located on the base station controller side ofthe network. These represent the standard 320-bit frames that are cominginto the system. Within the frames are the samples that were describedpreviously. The first of these TRAU frames that is being received byrouter 70 is indicative of the whole sample, which should be sentunchanged (as it is the first sample).

This first sample is stored by router 70 and then the second of theseTRAU frames is received by router 70. Now two samples can be compared(i.e. samples from one frame can be compared to samples from a previousframe). In this example, samples 2-9 are the same and, hence, do nothave to be transmitted on the backhaul. An IP over long-haul element 80is provided that illustrates how the data is actually transmitted acrossthe backhaul. As identified earlier, the first TRAU frame is stilltransmitted over the backhaul. However, the second TRAU frame is handleddifferently, as the algorithm of the present invention can readilyidentify this opportunity for suppression/compression. In the secondpacket that is being sent, samples 2-9 are not included. Only samples 1and 10 are being sent in the second packet because only those samplesare different between the two packets.

Hence, when samples between two frames are different, then the samplesare included in the packet and sent across the backhaul. When samplesare the same, then there is no need to send them over the backhaul. Therepeating samples only need to be played back and not transmitted overthe backhaul. Stated in anther way, only the “deltas” are transmittedover the backhaul. The delta reflects the difference in a comparison ofthe bits that would be in the same position of the previous frame.

FIG. 5 is a simplified flowchart illustrating an example flow associatedwith the present invention. Before turning to that FIGURE, at this pointin the discussion, the audience should recognize that in a typical GSMnetwork, voice conversations, data, and control information areformatted into frames described by various ETSI (e.g. GSM 08.60, GSM8.61) standards and/or proprietary vendor specific formats. The framesare then time-division multiplexed into 8 Kbps, 16 Kbps, 32 Kbps, or 64Kbps subchannels (i.e. subrates) and transmitted on an E1 or T1communications facility.

In order to reduce backhaul expenditures, a backhaul optimization methodis tendered here that provides significant bandwidth savings, whilemaintaining low latency end-to-end transmission for all possible frametypes. According to such a method, backhaul packets are created thatinclude a fixed length presence mask. The presence mask identifies thenumber and position of data samples that are to be included in thebackhaul packet. This presence information represents transmissionoverhead that could otherwise be used for transmitting user sample data.

In consideration of an example implementation, the presence mask is 256bits, which may consist of all one bits. The backhaul packets areencapsulated in HDLC and transmitted at a rate of 500 packets persecond. According to the methods defined by HDLC, an extra zero bit isperiodically inserted after five (5) consecutive one bits. Therefore,the amount of additional overhead that may be introduced by HDLC is 51bits: per backhaul packet, or 25500 bits per second. (Although thesemetrics may vary considerably based on specific implementations. Theaudience should appreciate that all of the numeric features and metricsmay be altered considerably, while still enjoying the benefits of thepresent invention.)

In practice, when the amount of voice traffic is minimal, the amount ofoverhead introduced by zero bit insertions is negligible. However, whenthe amount of voice traffic is large and the possibility of congestionexists, the amount of overhead introduced by zero bit insertion issignificant. Since the data sample size is 16 bits per sample, if theeffects of zero bit insertion could be mitigated for large packets, asavings of 3.19 samples per backhaul packet could be achieved. Thistranslates into three additional voice calls that can be transmittedbefore data loss would occur due to congestion.

The present invention proposes a method that mitigates the number ofconsecutive one bits that will occur in sequence by inverting themeaning of the presence mask bits for odd/even bits as indicated. Anexample formatting of such a protocol may be represented as follows:

-------- Transmit --------  build presence_mask in temp_pmask_buffer  if(vers2_uses_new_presence_mask_scheme) {   temp_pmask_buffer XOR0x55555555 /* invert odd bits */  }  Copy temp_pmask_buffer intobackhaulPak and transmit  --------  Receive  --------  Copypresence_mask from backhaulPak into temp_pmask_buffer  if(vers2_uses_new_presence_mask_scheme) {   temp_pmask_buffer XOR0x55555555 /* invert odd bits */  }

[In this example, the temp_pmask_buffer is used to save data into samplebuffers.]

More generally, this procedure is reflected by FIG. 5, which begins atstep 100 where a presence mask is built; this presence mask is about tobe transmitted along the backhaul. At step 102, if the sample is to beincluded, then the sample is marked as present, whereby the presence bitis used to indicate such. The present invention essentially inverts themeaning of the presence bit on every other bit. In cases where a ‘1’ isused to signify that the mask is included and a ‘0’ that it is notincluded, then a congestion problem arises.

To further elaborate on this issue of congestion, consider a situationwhere a large mask is generated (e.g. where all samples are included).This yields a string of ‘1’ bits. Hence, a string of 256 one-bits couldbe present. In this specific instance, this could translate into up to 6additional bytes of bits that are added due to zero bit insertion.

Step 104 addresses a typical HDLC scenario. In zero-bit insertion forHDLC, at the lowest level, after 5 one-bits, the link will automaticallyinsert another bit time for inserting a zero-bit. Thus, if a string of256 one-bits is present, then the bit times to transmit this databecomes excessive (e.g. greater than 300 bits in this example).

Therefore, in this instance, the problem is encountered when a bit maskis full of included samples. The byproduct of this scenario is anexceptionally large packet that is further encumbered by an overheadmask, which occupies additional bit times (about 51 bits in thisexample). The final result of this problem is premature/unnecessarycongestion. The present invention addresses this predicament byreversing the meaning of the bit mask at step 106. In an effort toreduce processing, a simple exclusive OR (XOR) operation could beemployed on the header, which is a fixed length field.

This operation mitigates the overhead effects of zero-bit insertion,which adds a zero-bit after five consecutive one-bits. For example, ifthe first sample is a one-bit then this would indicate that, indeed, ithas been included. For the second sample, a zero-bit would signify thatit is included. For the third sample, a one-bit would mean it isincluded and so forth. Now, if there is a long string of included bitsamples, where a big frame is present, the bits are being inverted suchthat once the physical layer is addressed, zero-bit insertion is nolonger necessary in HDLC, as reflected in step 108. By reducing theeffects of the zero-bit insertion, then the backhaul is free to transmitmore voice/data samples, which offers considerable bandwidth savings.This is reflected by step 110.

Note that in an alternative embodiment of the present invention, aprocess could be used that determines the meaning of the current bitbased on the previous bit. This could include an inversion operation orsome other form of logic (e.g. in conjunction with a non-return-to-zeromethod). However, this protocol would be more sophisticated and create aslightly more challenging implementation issue.

It should be noted that some of the steps discussed in the precedingFIGURES may be changed or deleted where appropriate and additional stepsmay also be added to the process flows. These changes may be based onspecific communication system architectures or particular networkingarrangements or configurations and do not depart from the scope or theteachings of the present invention.

Although the present invention has been described in detail withreference to particular embodiments illustrated in FIGS. 1 through 5, itshould be understood that various other changes, substitutions, andalterations may be made hereto without departing from the spirit andscope of the present invention. For example, although the presentinvention has been described with reference to a number of elementsincluded within communication system 10, these elements may berearranged or positioned in order to accommodate any suitable routing,compression, and suppression techniques. In addition, any of thedescribed elements may be provided as separate external components tocommunication system 10 or to each other where appropriate. The presentinvention contemplates great flexibility in the arrangement of theseelements as well as their internal components.

In addition, although the preceding description offers a solution to beimplemented with particular devices (e.g. aggregation node 22 and cellsite element 18) and protocols (e.g. HDLC), the compression/suppressionand bit insertion mitigation protocols provided may be embodied in afabricated module that is designed specifically for effectuating thetechniques discussed above. Moreover, such a module may be compatiblewith any appropriate protocol, other than those discussed herein, whichwere offered for purposes of teaching and example only.

Numerous other changes, substitutions, variations, alterations, andmodifications may be ascertained to one skilled in the art and it isintended that the present invention encompass all such changes,substitutions, variations, alterations, and modifications as fallingwithin the scope of the appended claims.

1. An apparatus for communicating data, comprising: a cell site elementassociated with a base transceiver station and operable to receive aplurality of bits associated with a communications flow, wherein thecell site element is further operable to determine whether one or moresamples included in the flow should be suppressed, and wherein the cellsite element is further operable to suppress a selected one or more ofthe samples if the selected samples are similar to previously receivedsamples, and wherein the cell site element is further operable to invertone or more selected header bits.
 2. The apparatus of claim 1, whereinthe cell site element is further operable to position unique samplesthat are included in the flow in a super-frame to be communicated to anext destination.
 3. The apparatus of claim 2, wherein the uniquesamples may be received and evaluated in order to restore a plurality ofbits associated with the communications flow.
 4. The apparatus of claim2, wherein the selected samples reflect patterns that correspond to oneor more data segments that are common to an associated network.
 5. Theapparatus of claim 4, wherein the data segments correspond to silencedata, idle data, control data, repetitive voice data, or user data. 6.The apparatus of claim 2, wherein the cell site element is operable toignore a framing protocol associated with the flow.
 7. The apparatus ofclaim 2, wherein the selected bits are odd bits and the inversionreduces overhead that is generated by a zero-bit insertion operation ina High Level Data Link Control (HDLC) protocol.
 8. The apparatus ofclaim 2, wherein the selected header bits are part of a header, whichhas a fixed length field.
 9. The apparatus of claim 2, wherein the cellsite element includes a dynamic suppression element that is operable toperform the suppression and positioning operations.
 10. The apparatus ofclaim 2, further comprising: an aggregation node associated with a basestation controller and operable to communicate with the cell siteelement and to receive the super-frame.
 11. A method for communicatingdata, comprising: receiving a plurality of bits associated with acommunications flow; determining whether one or more samples included inthe flow should be suppressed; and suppressing a selected one or more ofthe samples if the selected samples are similar to previously receivedsamples, wherein the cell site element is further operable to invert oneor more selected header bits.
 12. The method of claim 11, furthercomprising: positioning unique samples that are included in the flow ina super-frame to be communicated to a next destination.
 13. The methodof claim 12, further comprising: receiving the unique samples; andevaluating the unique samples in order to restore a plurality of bitsassociated with the communications flow.
 14. The method of claim 12,wherein the selected samples reflect patterns that correspond to one ormore data segments that are common to an associated network.
 15. Themethod of claim 14, wherein the data segments correspond to silencedata, idle data, or control data, repetitive voice data, or user data.16. The method of claim 12, further comprising: ignoring a framingprotocol associated with the flow.
 17. The method of claim 12, whereinthe selected bits are odd bits and the inversion reduces overhead thatis generated by a zero-bit insertion operation in a High Level Data LinkControl (HDLC) protocol.
 18. The method of claim 12, wherein theselected header bits are part of a header, which has a fixed lengthfield.
 19. Software for communicating data, the software being embodiedin a computer readable medium and comprising computer code such thatwhen executed is operable to: receive a plurality of bits associatedwith a communications flow; determine whether one or more samplesincluded in the flow should be suppressed; and suppress a selected oneor more of the samples if the selected samples are similar to previouslyreceived samples, wherein the cell site element is further operable toinvert one or more selected header bits.
 20. The medium of claim 19,wherein the code is further operable to: position unique samples thatare included in the flow in a super-frame to be communicated to a nextdestination.
 21. The medium of claim 20, wherein the code is furtheroperable to: receive the unique samples; and evaluate the unique samplesin order to restore a plurality of bits associated with thecommunications flow.
 22. The medium of claim 20, wherein the code isfurther operable to: ignore a framing protocol associated with the flow.23. The medium of claim 20, wherein the selected bits are odd bits andthe inversion reduces overhead that is generated by a zero-bit insertionoperation in a High Level Data Link Control (HDLC) protocol.
 24. Themedium of claim 20, wherein the selected header bits are part of aheader, which has a fixed length field.